A variety of techniques and procedures are used to process tissue. In some applications, chemicals or enzymes are added to tissue to break-up larger clumps or aggregates of tissue into smaller and smaller pieces. For example, digestive enzymes such as collagenase, trypsin, or dispase are used to digest tissue such as adipose tissue. Such enzymatic processing typically involves washing, followed by enzymatic degradation and centrifugation. This enzymatic approach may suffer from variability due to different activity levels of the digesting enzymes. Moreover, these methods require added costs for reagents including expensive enzymes that are derived from bacteria and take considerable time to complete, as well as additional processing and/or wash steps to minimize the effects of enzyme contamination.
Non-enzymatic approaches have also been developed to process tissue, including fat tissue. For example, ultrasonic cavitation has been proposed for the isolation of stromal vascular fraction from adipose tissue. See U.S. Pat. No. 8,440,440, which is incorporated in its entirety by reference herein. Still other methods involve the use of beads to homogenize adipose tissue such as that disclosed in International Patent Publication No. WO2014-036094, which is incorporated in its entirety by reference herein. U.S. Pat. No. 9,580,678 (which is incorporated in its entirety by reference herein) discloses a microfluidic tumor dissociation device that uses a plurality of serially arranged channels or stages with expansion and constriction regions that are used to break-up the tumor tissue. A syringe pump is used to pass tumor tissue back-and-forth through the microfluidic device.
Processing of tissues such as fat tissue has particular importance to the field of plastic and reconstructive surgery where fat tissue is transferred from one location to another to fill soft tissue defects (i.e., fat grafting). Cell-assisted lipotransfer (CAL) is a technique that involves the addition of the stromal vascular fraction (SVF) to fat grafts, and has resulted in significant improvements in fat graft retention. Typically, the SVF is harvested from adipose tissue by a short digestion step using the enzyme collagenase. More recently, a technique called ‘nanofat grafting’ was developed, whereby standard lipoaspirate is homogenized by manually passing it vigorously between two connected syringes, and then reinjecting the homogenized lipoaspirate in human patients for the correction of superficial rhytides and pigmentation. It was also found that the nanofat processing methods can serve as a means of mechanically dissociating SVF while also stressing the cells to generate multipotent or even pluripotent populations. For example, nanofat-derived SVF is known to have a greater proportion of mesenchymal stem cells (MSCs), adipose derived stem cells (ADSCs), endothelial progenitor cells (EPCs), and Muse cells. It was postulated that the amount of stress that is applied to cells directly correlates with stem-like properties.
MSCs, for example, may be used to treat diabetic ulcers. Current treatments of diabetic foot ulcers, such as allografts, are costly and may not be effective due to the potential rejection by the patient. If such ulcers are left untreated, patients have to undergo limb amputation which, in turn, leads to additional health complications. One innovative solution to treat these ulcers is through the use of MSCs for the direct treatment of these ulcers. However, current approaches of obtaining such cells are lengthy, complicated, and yield variable results in terms of cell yield, quantity and reproducibility. There is a need for quick and cost-effective methods for obtaining processed tissue.